Root&#39;s blowers, in particular for suction purposes



Jan. 29, 1957 o. HERSCHMANN 2,779,532

ROOTS BLOWERS, IN PARTICULAR FOR SUCTION PURPOSES Filed Sept. 30, 1955 FIG. 2.

INVENTOR OTTO HERSCHMANN WWW ATTORNEY.

United States Patent ROOTS BLOWERS, IN PARTICULAR FOR SUCTION PURPOSES Otto Herschmann, Hannover, Germany Application September 30, 1955, Serial No. 537,857

1 Claim. (Cl. 230-141) The present invention relates to a Roots blower which, due to its particular construction, is suited for suction purposes.

Roots blowers are employed for different operations, in particular for supercharging internal combustion engines. Furthermore, it has been proposed to employ the blowers provided on motor vehicles for the operation of vacuum plants, as for instance, for milking purposes. Experience has shown, however, that due to the vacuum on the suction side the oil contained in the pump and required for lubricating the bearings and the gears is also sucked up and forced away. Consequently, either the blower journals run dry or, if the journals are in communication with the engine oil circuit, the engine oil and lubricating oil was sucked up. In the shipbuilding industry it has already been proposed to pressure-feed the medium to a chamber of the rotor shaft separated by seals, to prevent the air under atmospheric pressure from being sucked into the housing when a vacuum exists in the housing, and to prevent the oil from flowing from the journal into the stufling box. Furthermore, it is known to connect the chamber between the stufiing box and the journal with the suction side of a pump to control the flow of the bearing lubricating oil.

It is, therefore, one object of the present invention to provide a blower which prevents the lubricating oil from being sucked up and in which the chamber of the shaft journal facing the blower rotor and separated by a seal is connected with the pressure chamber of the pump in any position of the blower rotors. Thus the part of the shaft journal facing towards the blower rotors always is subjected to the effect of compressed air. Due to the suction effect a small amount of compressed air is lost. In any case, however, no lubricating oil is sucked up. It suffices to design the passage sections for the compressed air comparatively small so that the leak air volume is small and a sealing means is formed against sucking up the oil.

It is another object of the present invention to provide a connection between the pressure chamber of the blower and the portion of the shaft journal facing towards the blower rotor by a groove, a channel, or the like, arranged in the front wall of the blower. It is important that the channel, in any position of the blower rotors, is outside the line of action of the two rotors so that no short cut occurs between the pressure and the suction side of the blower.

With these and other objects in view which will become apparent in the following detailed description, the present invention will be clearly understood in connection with the accompanying drawing, in which:

2,779,532 Patented Jan. 29, 1957 ICC . 2 Fig. l is a top plan view on the front wall of the blower, supporting the rotor journals;

Fig. 2 is a sectional view along the lines'2-2 of Fig. l; and

Fig. 3 is a sectional view along the lines 33 of Fig. 1, part of the blower rotors and the journals being illustrated in section.

In the lateral wall 1 of the blower housing the shaft ends 3 are journalled through means of ball bearings 2. On the portion of the shaft ends 3 inside the blower the rotors 4 are arranged. A labyrinth seal 5 is interposed between the ball bearings 2 and the inner blower chamber, said seal 5 preventing the oil from flowing into the blower housing. To the outside the journal is closed by a cap 6. The chamber 7 provided in the front side of the lateral wall 1 or, respectively, in the cap 6 is filled with lubricating oil. The rotors 4 rotate in the direction of the arrows shown in Fig. 1 so that the vacuum develops above the blower (Fig. 3), and the compressed air is discharged in downward direction, as indicated by arrows.

According to the present invention the pressure chamber'8 of the blower is in communication with the journals of the rotors through means of a passage 9 arranged in the front side of the lateral wall 1.

A recess 10 in the shaft end 3 provides for a small annular chamber between the labyrinth seal 5 and the rotor 4, said annular chamber, by bridging the journal, being connected to the passage 9 leading to the pressure chamber, through means of a recess 11. Thus, the journal, through means of the passage 9, is in communication with the pressure chamber of the blower. A vacuum which may exist in the suction chamber 12 of the blower may be conducted up to the annular channel 10 only, through the gaps remaining between the front side of the lateral wall 1 of the housing and the lateral wall of the rotor 4. Since the channel 10, through means of the passage 9, is connected with the pressure side of the blower, the labyrinth seal 5 prevents the lubricating oil from being sucked up.

It is important, however, that the passage 9 is arranged so that the dotted line of action 13 of the blower rotors 4 is not traversed (Fig. l). A short-cut between the pressure chamber and the suction chamber is thus eliminated.

While I have disclosed one embodiment of the present invention, it is to be understood that this embodiment is given by example only and not in a limiting sense, the scope of the present invention being determined by the objects and the claim.

I claim:

A Roots blower comprising a pumping chamber, cooperating blower rotors rotatably mounted in said pumping chamber, each of said rotors having a shaft extending from each side thereof, a bearing including lubricating means mounted on opposite sides of said pumping chamber and supporting said respective shafts, a seal surrounding said shaft and disposed between said bearing and the end faces of the corresponding of said blower rotors, and a groove formed in the inner walls of said pumping chamber adjacent the end faces of said blower rotors and disposed outside the line of action of said blower rotors, and a recess communicating with said pumping chamber adjacent said groove, said groove being in communication with the pressure side of said blower and said recess being in communication with said groove, and means providing a lower pressure on the bearing side of said seal than the pressure on the pumping chamber side --of said 'sel, thereby, preventing a flow of -said lubricating means from said bearing thro'ugh said seal in the direction toward said pumping chamber and the suction side of said blower.

References Cited in the file of this patent UNITED STATES PATENTS 4 Carrier Aug. 16, 1932 Gregg July 17, 1934 Hallet't Sept. 17, 1935 Sherwood Sept. 30, 1941 Halliday Mar. 17, 1942 Jacobsen June 14, 1949 Jack May 2, 1950 Miller May 29, 1951 Jacobsen Jan. 29, 1952 Brill et a1. Dec. 2, 1952 Lauck Apr. 27, 1954 Rand Sept. 25, 1956 

